Timing pulse generator



Aug. 5, 1952 Filed oct. 4, 195o ZSE-SHETI ATTORNEY Patented Aug. 5, 1952UNITED STATES PATENT OFFICE (Cl. Z50-27) 3 Claims. 1

This invention relates to the generation of timing pulses andparticularly to means for 'increasing the accuracyof the time spacing ofthese pulses.

In one known method of generating such pulses advantage is taken of thehigh accuracy of available standard frequencies by counting the cyclesof such a signal, generating one timing pulse for each hundredth,thousandth or millionth cycles as the case requires. For example, whenusing a standard frequency of 1 mc. and generating one pulse for eachmillion cycles of the signal, the timing pulses will be spaced onesecond apart. This is readily accomplished by means of a p-lurality ofdecade counting circuits serially connected together to count the numberof cycles of the source in the pulse spacing interval required andproduce one pulse at the output of the slowest cycling decade.

In such a system the degree of accuracy obtainable is limited 'by thevariations in the transit time of the signal pulses in passing throughthe successive decades.

The object of this invention is to eliminate the errors due to thesetransit time variations.

Applicants accomplish this object by insertingnormally closed gatingmeans between the standard frequency source and a pulse output circuit,and providing means for opening the gate only on a specific cycle of thestandard frequency.

More specifically, to a system of the .type described above there isadded a series of trigger circuits, one for each counting decade, thesecircuits being serially connected in a backward sense relative lto thecounting decades. A triggering connection is vprovided from the input ofeach decade to the corresponding trigger circuit 'and a similarconnection made between the output of the slowest cycling decade and thefirst trigger circuit to give an output timing pulse at the last triggercircuit which is independent `of variation in the transit time of pulsesthrough the decades.

Other objects and advantages will -be apparent from the followingdetailed specification taken in conjunction with the attached drawingsin which:

Fig. l is a yschematic diagram of the invention;

Fig. 2;is a chart of the time sequence of operation of the triggercircuits used in the invention.

As may be seen in Fig. 1, a standard frequency source 'l is used as thebasis for the generation of the timing pulse. This frequency shouldpreferably be high, for example, one megacycle, in order to obtain atiming pulse having the sharp definition required to provide an accuratetime interval. If a one megacycle `frequency 'is not available, thestandard frequency may be 'changed to this value by any conventionalfrequency converting means 3. One way in which this conversion may bea^comp`lished is through the use of a harmcnic generator as described inthe YBell System Techni-cal Journal, page 437, dated Octoner The onemegacycle frequency thus obtained is then passed through an amplifier :9before entering the timing `pulse apparatus through conductor l0. The`incoming standard signal neX-t passes through a plurality of countingdecades l through 6. These are conventional counter units and may :be ofthe vtype described in the article lentitled Electronic Counters by I.E. Grosdoff, ,RCA Review, September 1946. Each individual decadecomprises a conventional four-stage cascaded trigger circuit asindicated in deca-de I, in which feedback is added between the secondand third stages and between the third and fourth stagesto reduce thenormal 16 counts to 10 counts vper decade output pulse and therebyconvert the unit from the binary system to the decimal type. Thesedecades use a conventional count indicati-ng lsystem with neon lampsbehind a numbered strip interconnecting the plate circuits to indicatethe electrical posi.- tions of the decades.

Counting decades l through 6 are connected in series through connectingleads 2l, 2.2, 23 24, and 25 so that each decade after decade .6receives the output pulse of each previous unit. As a result, with a onemegacycle signal input, each decade of the six will pass through zeroand cycle only ,-10- as vfast as the preceding decade, and the slowestunit, decade il, will cycle only once for each ymillion cycles of thestandard frequency.

As shown in Fig. 1, the input signal .is impressed in each lcase ongrids 30 of the first stage of each `decade while the output is takenfrom the plate circuits 32 of the fourth or last `sta-ge of each decade.The individual decades are grounded fat .points 33 as shown.

it is possible to use ythe output pulse of decade I as a timing pulse,this pulse occurring once each second for the Vcombination of a onemegacycle standard frequency and a six decade counter. However, thepasage of .pulses derived from the standard frequency source through thesix counting decades is not under control, -and since there aretwenty-four trigger circuits in the six units, each having a nite timeof operation, it yis .obvious .that variations will occur in the passagetime of pulses through the decades.- These variations in the total timeof operation of the twenty-four circuits will adversely affect theaccuracy of any timing pulse taken from the output of decade I, and as aresult, timing pulses obtained in this manner are unsatisfactory forcounting operations where eXtreme accuracy is required.

To overcome this diiiiculty and to provide an accurate timing pulsewhich is largely independent of variations in pulse transit time throughthe decades, applicants have used a plurality of trigger circuitscorresponding in number to the counting decades and interconnected withthese decades. These trigger circuits are similar to those used in theindividual stages of the counting decades except that instead of havinga single input to the grids of the circuit, separate inputs are providedto enable the -circuit to be actuated by pulses from two separatesources. As shown, the individual circuits are grounded at points 34.The action of these trigger circuits I I through i6 in conjunction withcounting decades I through 6 is as follows:

Counting decade I, being the last of six decades,` cycles once eachsecond for an input signal of one megacycle. The output is a rectangularWave which is suitably diierentiated to give a positive and a negativepulse. The positive pulse is eliminated through a diode rectifier (notshown) While the negative pulse is fed through conductor 40 to the grid4I of trigger circuit II thus driving the upper half of the circuitincluding the plate 42 to non-conduction. The grid 4I and plate 42 arecross-connected to the grid 43 and plate 44 of the other half of thecircuit in the usual manner and, through conventional trigger circuitaction, the lower half of the circuit containing the plate 44 is drivento conduction. The output of counting decade 2, in addition to being fedinto counting decade I, is also fed through lead 45 to the grid 43.Decade 2 produces ten cycling pulses per second, each of -which tends todrive the lower half of trigger circuit II to non-conduction. However,on nine no eiect. It is only on the first pulse after the flower halfincluding the grid 43 and plate 44 has been driven to conduction by theoutput pulse from decade I that the pulse from decade 2 is operative tochange it from a conducting to a non-conducting state. When this lowerhalf is thus rendered non-conducitng, the upper half is caused to beconducting, and through the inherent inversion action of the circuit, anegative going output pulse will be produced.

It will thus be seen that the upper half of trigger circuit II,including plate 42, has been made non-conducting by the output pulsefrom decade I and subsequently made conducting by the output pulse fromdecade 2 next after the cycling of decade I. This triggering actionresults in a rectangular Wave output signal whose yleft Vhalf ispositive going and whose right half Y`is negative going. The wave isthen diierentiated to give rst a sharp positive pulse and then 'a sharpnegative pulse which reaches the trigger circuit I2. The positive pulsewill have no effect as it is eliminated by a diode rectifier, but thenegative pulse will reach the grid 4I of the circuit I2 to drive theupper half of the circuit to conduction.

The same triggering action `lust described in connection with circuit IIalso takes place in trigger circuits I2, I3, I4, and I5. In each casethe upper half of the circuit is first rendered non-conducting by theoutput pulse from the previous triggering circuit. These halves are thenplaced in a conductive state by the cycling pulses from decades 3, 4, 5,and 6 respectively which act on the lower grids 43 of the circuits.These actuating pulses are in each case the first cycling pulses afterthe cycling of the next slower decade.

The actuation of circuit I6 diiers slightly from that of the precedingtrigger circuits. In this case, the upper half of the circuit isrendered non-conducting by the output pulse from trigger circuit I5, butinstead of receiving the output of one of the counting decades to renderit conducting, it receives an actuating pulse direct from the standardfrequency source 9 through conductor 6i?. This pulse which drives thelower half of trigger circuit I5 to non-conduction is the pulse of thestandard frequency source next in time after this half has been renderedconducting by the triggering action of the output pulse from circuit I5on the upper grid 4i of circuit Iii.

In the case of trigger circuit I6 the rectangular wave output resultingfrom the triggering action is taken from the lower plate 44 instead offrom the upper plate 42 as in the previous trigger circuits.

The lower half of trigger circuit I6 therefore acts as a gate which isnormally closed by the interaction of the decades and trigger circuitsand is allowed by such interaction to be opened only on a specific cycleof the standard frequency.

The rectangular wave resulting from trigger circuit I6 is differentiatedby a suitable circuit (not shown) and thereby shaped to provide asuccession of sharply peaked positive and negative pulses. These pulsesare then fed into means for selecting pulses of a desired polarity, suchas an ampliiier 6I which is biased to cut off, causing the positivepulses to be amplified as desired whereas the negative pulses will notappear in the amplifier output in view of the cutoff bias. As a resultof the inherent inversion action of the amplier, the output B2 will be aseries of peaked negative timing pulses which occur at the rate of oneper second for the combination of a l megacycle standard signal and asix decade counter.

The ampliiier 6I may have more than out output for the timing pulse thusobtained. The use of multiple outputs enables the pulse generatingapparatus to act as a pulsing service unit simultaneously for aplurality of applications. Cathode follower type outputs are especiallysuitable in such a case since they effectively isolate the various pulseoutput circuits from each other and also provide a low impedance sourcefor the transmissionof the pulses. i rIhe result of the Presentapparatus is a sharp timing pulse which occurs once per desired unit oftime, this time being one second in the exampie here presented. Thebackward cascade arrangement of the triggering circuits with respect tothe counting decades insures that the timing pulse is produced by asingle specific cycle of the standard frequency signal, this speciiiccycle being the first one in time after the upper half of triggercircuit I5 has been driven to cutoif by the input pulse from circuit I5.

The manner in which the eiect of variations Ain transit time of pulsesthrough the counting decades is largely eliminated may be seen byreference to Fig. 2. This figure is a chart in which the shaded portions-represent the relative time during a one second cycle that the upperhalves of the six trigger circuits are in a nonconducting state. Theunshaded portions of the chart represent the time that the upper halvesof the trigger circuits are in a conducting state. The numberspertaining to the individual blocks represent the fractional parts of acomplete second that the upper halves of the trigger circuit are 'in the.two conditions shown, while the numbers at the vright oi the yblocks.represent the fractional :part of a complete second thatthese upperhalves are in a non-conducting state. The chart is kpredicated on theuse of a one megacycle standard :frequency in conjunction with a y6decade counter to give a pulse interval time of one second.

With reference to the .previous description, it has been shown that theinput pulses to the six counting decades, which represent the outputpulse from the previous next faster decade in all cases except .fordecade 6, drive the lower halves of the trigger circuits tonon-conduction and thereby cause a negative output pulse to be appliedimmediately to the succeeding trigger circuit. .The time intervalbetween this pulse being impressed on the bottom half of one circuit andthe arrival of the circuit output pulse to drive the upper half of thesucceeding circuit to nonconduction is normally only about ,-16microsecond. This action is therefore practically instantaneous and isso shown in the chart in Fig. 2.

With reference to Figs. 1 and 2, it will be seen that lthe upper half oftrigger circuit II is turned @olf by a cycling pulse from countingdecade I Aand is turned on by the next pulse in time arriving fromdecade 2. Even though there is a small variation in the time of itsbeing turned off, this will be of no importance as long as it is turnedoff `by the time the pulse from decade 2, next after the cycling pulsefrom decade I,

'reaches this circuit to drive the upper half to non-conduction. Thesame consideration prevails throughout the trigger circuits and sinceeven with normal variations the action of the conventional triggercircuit used is fast enough that each is always turned oif well inadvance 'of the arrival of the turn on pulses, the variations in time ofthe operation of the counting decades and trigger circuits may bedisregarded. In other words, every time the upper half of a particulartrigger circuit has been turned on by the `proper pulse, any variationsin time in the trigger or decade circuits preceding it may bedisregarded.

yThe only circuits with whose operational time variations we areconcerned are the circuits in the four stages of decade 6, plus triggercircuit I5 in connection with they driving of its lower half tonon-conduction and trigger circuit I6 in connection with the driving ofits lower half to conduction. 'I'o insure accuracy of the timinginterval, these six circuits must operate within a yperiod of onemicrosecond which is the time vbetween the pulse which cycles decade 6and the next pulse which turns on the lower half of circuit I6. Inpractice the voperating time of these circuits with normal care indesign is well under a microsecond with the result that the lower halfof trigger circuit I6 is always made conducting by the arrival of thenrst pulse in 6 'time Vfrom the .standard frequency source :after the-pulse which lcycled decade 6.

As long as the primary condition -of operation is met, i. e., that the-upper half of each trigger circuit shall have been renderednon-conductive by the cycling pulse of a particular decade by the timeits turn on -pulse arrives, the various triggering actions will alwaystake place on exactly thesame pulses of the timing pulse generationsequence. The result will be -that the output pulse from trigger'circuit I6 will always be produced by -a-specic cycle of the `standardfrequency. This means that the timing pulses `which are the output ofthe system always 'have exactly the same interval of time between themand may therefore be termed accurately periodic.

It should be borne in mind that the turn on pulses referred to are takenfrom the input of the various decades. In the case of decades I through5, this pulse is the iirst cycling pulse after the cycling of the nextslower decade. In the case of decade, this pulse is the first pulse ofthe standard frequency after the pulse which cycles decade 6.

In connection with the above, the number of the incoming pulses, afterthe cycling of decade I, which drive the upper halves of the `varioustrigger circuits to conduction areas follows:

III 100,000 I2 10,000 I3 V1,000 I4 .100 I5 .10 1.6 l1

From the above'it .is apparent that it is pulse 111,110 of the incomingsignal which drives the upper half of trigger circuit IS tonon-conduction. This circuit is then driven to conduction bythe nextincoming pulse from the standard frequency source which is 111,111. Thepresent circuit has been designed so that it has to be pulse 111,110which drives the upper 'half of trigger circuit I6 to non-conduction aslong as the upper half cf-every preceding trigger circuit has Ybeenturned off before the arrival of vvthe turning on pulse, from itsactuating decade, next after the cycling of the next slower decade. Theupper half of trigger circuit I6 ris also always turned on by pulse111,111 oi the input standard signal provided that pulse 111,110 haspassed through the six circuits in decade 6 and trigger circuits I5 andI6 to turn off the upper half of circuit I6 within one microsecond,which is the time required for the arrival of the next succeeding pulse.

The sequence of events yof the various cycles of the incoming standardsignal is' as follows:

Pulse 1starts the counting sequence VPulse 1,000,000--cycles all decadesto zero includ- .operation of the four circuits included in decade -6and in trigger circuits I5 and I6 would result in variations in thewidth of the rectangular wave output obtained from trigger circuit I6inasmuch as the location zof .the .left side -of .the

`accedas wave would be dependent on this time, whereas the right sideresults from the action of cycle 111,111 of the standard signal whichmay be considered as non-varying. However, by causing the left half ofthe rectangular wave output to be negative going and the right half ofthe wave to be positive going, and then eliminating the negative pulsesresulting from differentiation of the rectangular wave by passingthrough the amplifier 9 biased at cutoff, the effect of these variationsis eliminated. This is accomplished by taking the output of triggercircuit lqfrom its lower plate fill instead of from Vtheupper plate 42as in the previous circuits to make the left half of the rectangularwave result in a negative going pulse.

When the pulse generatoris used for the first time, one or output pulsesfrom decade I5 may occur at irregular intervals, depending on theoriginal state of conduction of the various trigger circuits. In anyevent a pulse will occur at 111,111 cycles after decade l has cycled,and remaining output pulses from circuit i5 will occur at exactintervals.

Pulses from the input to the counting decades do not disrupt the timinginterval after the first regularly occurring pulse by prematureactuation of the triggerfcircuits through leads 45 since the lowerhalves of these circuits which they reach are in a non-conducting state,except for the regular chain sequence, and hence are normally unaffectedby the negative actuating pulses.

Timing pulses generated as herein described are independent ofvariations in the transit time of pulses through the counting apparatus.backward cascading'of the trigger circuits with respect to the countingdecades produces a timing pulse having an accuracy essentially equal tothat of the standard frequency, the latter usually being stable to onepart in 10S.

By varying the number of decades used for a given input frequency, itwould be possible to provide accurate timing pulses having a frequencyof 1, 10, 100, or 1000 per second. It is likewise possible Vto providetiming pulses occurringonce L..

each 10 seconds, one each 100 seconds, etc. This result maybeaccomplished by adding or subtracting decades and correspondingtrigger circuits from the left side of the pulse generating systemlocking at Fig. 1.

The periodic timing pulses thus generated may -be used in anyapplication requiring an accurately timed interval or pulse, cr in anyapplications where a train of such timing pulses may be desirable. pulseproduced in this manner would be in the direct counting of the frequencyof an oscillatory system to provide an accurate timing interval duringwhich the count of the unknown frequency takes place. Such a frequencycounting system is described in co-pending applicationk Serial No.188,456, filed October 4, 1950.

It is to be understood that the above described arrangements are simplyillustrative of the application of the principles of the invention.Numerous other arrangements may be readily devised by those skilled inthe art which will embody the principles of the invention and fallwithin the spirit and scope thereof.

What is claimed is:

1. n a pulse generating system the combination with a source of standardfrequency and a plurality of serially connected decade circuits forcounting the cycles of the frequency and producing at the output of eachcircuitone pulse for The Gne typical application of a timing. i

lil

8 each counting cycle of the decade, of a pulse out# put circuit,normally closed gating means between the slowest cycling decade and theoutput circuit, and means independent of the counting means for openingthe gate cyclically on a specific selected cycle of the standardfrequency.

2. In a pulse generating system the combination with a source ofstandard frequency and a plurality of serially connected decade circuitsfor counting the cycles of the frequency and producing at the output ofeach circuit one pulse for each counting cycle of the decade, of a pulseoutput circuit, a normally closed gate circuit between the standardfrequency source and the out- 5 put circuit, means operated by an outputpulse from each of the decade circuits for conditioning the gate circuitcyclically to open on a selected cycle, and means independent of thecounting means for opening the gate.

3. In a pulse generating system the combination with a source ofstandard frequency and a plurality of serially connected decade circuitsfor counting the cycles of the frequency and producing at the output ofeach circuit one pulse for each counting cycle of the decade, of atrigger circuit for each decade circuit, a triggering connection fromthe input of each decade circuit to the corresponding trigger circuit,and a like connection between the output of the slowest cycling decadeand its trigger circuit, said triggering circuits being seriallyconnected together in backwardly acting relation with respect to thedecade circuits.

4. In apparatus for generating a periodic timing pulse, the combinationwith a source of standard frequency and a plurality of seriallyconnected decades for counting the cycles of the frequency, of acorresponding number of trigger circuits serially connected together inbackwardly acting relation with respect to the decade circuits, with thefirst circuit receiving a rst impulse from the slowest decade and asecond oppositely acting pulse from the next faster decade, theintermediate circuits receiving corresponding first pulses from thepreceding circuit and corresponding second pulses from succeeding fasterdecades, and the last circuit receiving its first pulse from thepreceding circuit and itsV second pulse from the standard frequencysource.

5. 1n a pulse generating system the combination with a source ofstandard frequency, means for converting said frequency to a desiredvalue, and a plurality of serially connected decade circuits forcounting the cycles of the frequency and producing at the output of eachcircuit one pulse for each counting cycle of the decade, of a triggercircuit for each decade circuit, a triggering connection from the inputof each decade circuit to the corresponding trigger circuit, and a likeconnection between the output of the slowest l cycling decade and itstrigger circuit, said triggering circuits being serially connectedtogether in backwardly acting relation with respect to the decadecircuits, and a pulse output circuit connected to the output of the lasttrigger circuit.

6. In apparatus for generating a periodic timing pulse, the combinationwith a source of standard frequency and a plurality of seriallyconnected decades for counting the cycles of the frequency, of acorresponding number of trigger circuits serially connected together inbackwardly acting relation with respect to the decade circuits, with thefirst circuit receiving a first pulse from the slowest decade and asecond oppositely acting 'pulse from'the next faster decade, theintermediate circuits receiving corresponding rst pulses from thepreceding circuit and corresponding second pulses from succeeding fasterdecades, and the last circuit receiving its first pulse from thepreceding circuit and its second pulse from the standard frequencysource, said second pulses be-r ing the next in time after the cycling'of the decfy ades fed by the second pulses, the trigger circuits beingadapted to trigger on said first pulses before the arrival of the secondpulses.

7. In apparatus for generating a periodic timing pulse, the combinationwith a source of standard frequency and a plurality of seriallyconnected decades for counting the cycles of the frequency and producingat the output of each decade one pulse for each counting cycle of thedecade, of a corresponding number of trigger circuits serially connectedtogether in backwardly acting relation with respect to the decadecircuits and each having two halves each including a grid and plate,with the first circuit receiving an inif tial pulse from the slowestdecade on a rst grid and a subsequent pulse from the next faster decadeon its second grid, the intermediate circuits receiving correspondinginitial pulses from the first plates of the preceding circuit on theirrst grids and corresponding subsequent pulses from succeeding fasterdecades on their second grids, and the last circuit receiving an initialpulse from the rst plate of the preceding circuit on its rst grid and asubsequent pulse from the standard frequency source on its second grid.8. In apparatus for generating a periodic timing pulse, the combinationwith a source of standard frequency, means for converting said frequencyto a desired value, and a plurality of serially connected decades forcounting the cycles of the frequency and producing at the output of eachdecade one pulse for each counting cycle of the decade, of acorresponding number of trigger circuits serially connected together inbackwardly acting relation with respect to the decade circuits and eachhaving two halves each including a grid and plate, with the firstcircuit receiving an initial pulse from the slowest decade on a firstgrid and a subsequent pulse from the next faster decade on its secondgrid, the intermediate circuits receiving corresponding initial pulsesfrom the first plates of the preceding circuit on their rst grids andcorresponding subsequent pulses from succeeding faster decades on theirsecond grids, the last circuit receiving an initial pulse from the rstplate of the preceding circuit on its rst grid and a subsequent pulsefrom the standard frequency source on its second grid, the output pulsesof the last circuit being taken from the second plate; and an outputcircuit for the pulses including means for selecting pulses of a desiredpolarity.

EARL L. CHA'ITERTON. ANDREW S. HEGEMAN, JR.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,166,688 Kell July 18. 19392,519,184 Grosdoi Aug. 15, 1950

